Worms Make $3M Meal of Bridge

Worms are the likely culprits behind $3 million in damage that will delay a $40.6 million coastal bridge project in southern California by a year.

Crews working on replacing an aging railroad bridge over the Santa Margarita River in Oceanside discovered that portions of temporary wooden supports, or "falsework," had failed, falling down before concrete molds properly set and spreading tiny cracks through the superstructure.

Builders suspect that marine worms dug into the wooden supports, weakening them. Now, workers are removing and replacing the concrete for the 500-foot-long main bridge structure.

American Railway Engineering and Maintenance-of-Way Assoc.

Part of a $40.6 million bridge replacement project in San Diego County has to be completely removed and replaced after concrete failed on the main bridge structure.

Bridge Failure

A joint venture of Flatiron Construction Corp. and Herzog Contracting Corp. is the primary contractor for the project, which includes replacing an existing steel truss, single-track railroad bridge with a new, reinforced-concrete, double-track bridge.

The new 755-foot-long bridge consists of a 500-foot main bridge structure that spans the Santa Margarita River and carries part of the second busiest intercity rail corridor in the nation, the LOSSAN (Los Angeles-San Diego-San Luis Obispo).

The failure was discovered as crews were preparing to place the new concrete deck on the main bridge. The contractor then opted to remove and replace the parts of the bridge that were completed before the supports failed.

However, the piers and footings of the bridge, with foundations installed as deep as 200 feet below the river bottom, were not damaged and will remain in place.

Water Damage Potential

The damage could allow water to enter the concrete, degrading the structure and reducing its 100-year lifespan, David Hicks, a spokesman for the San Diego Association of Governments (SANDAG), told the Los Angeles Times.

SANDAG

The failed concrete is delaying the project by up to a year, costing approximately $3 million.

The bridge's existing timber trestle approach structure will also be replaced with a 255-foot, pre-cast box girder trestle approach that spans a tidal marsh.

Flatiron has a 60 percent share of the project and is responsible for the bridge construction and earth work; Herzog is responsible for track, signal and drainage work.

SANDAG expects the cost of partial demolition and replacement from the falsework failure will be handled by the contractor's risk insurance company.

Bridge History

Located north of Oceanside and within the U.S. Marine Corps Base Camp Pendleton, the Santa Margarita River Bridge dates back to 1916. The existing steel bridge and wooden trestle approach were built between 1916 and 1927 after storms and flooding washed away major segments of the bridge.

The bridge sits adjacent to Interstate 5, and the new structure is designed to withstand 100-year flood events. Construction is now expected to be completed in mid-2014.

American Railway Engineering and Maintenance-of-Way Assoc.

The rail bridge being replaced carries part of the 351-mile LOSSAN rail corridor, the second busiest intercity rail corridor in the nation.

According to SANDAG, the association plans to make $820 million in improvements to the 60-mile stretch of the LOSSAN in San Diego County.

SANDAG is governed by a Board of Directors composed of mayors, councilmembers, and county supervisors from the region’s 19 local governments.

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